Area Forecast Discussion
Issued by NWS Rapid City, SD
Issued by NWS Rapid City, SD
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401 FXUS63 KUNR 122336 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 536 PM MDT Sun May 12 2024 .KEY MESSAGES... - Chances for thunderstorms late this afternoon into this evening. Severe weather is not anticipated. - Smoke from wildfires will filter into the region this evening with chances for degraded air quality in some areas. - Warm and unsettled conditions with near daily chances for showers and afternoon thunderstorms. Best chances for precip is Monday night through Tuesday. && .DISCUSSION...(This Evening Through Sunday) Issued at 139 PM MDT Sun May 12 2024 Upper low is centered over CO with weak cool front/sfc trof draped across eastern into south central SD. Not much cold air is filtering in behind the front with temperatures in the region in the low to mid 70s. The front has been advecting some light smoke from Canada into the FA, with some stations in central SD reporting moderate to unhealthy AQ. A few showers and storms have popped up over the BH over the past couple of hours. Weak instability of 250-500 J/kg CAPE will continue to support slight chances for thunderstorm development this afternoon, especially in the southern BH thanks to eddy convergence due to the northerly winds. Not anticipating any severe weather as shear is minimal (generally 15 to 20 kts effective shear) though inverted V profiles and DCAPE values of 800-900 J/kg are supportive of strong, gusty winds in some of the stronger storms. CAMS hint at a small line of convection moving southeast across the BH after 00z. Again, the environment isn`t expected to be conducive to severe storms. Conditions should clear out later tonight as a weak upper ridge builds into the region. This should provide decent viewing conditions for the northern lights (should they appear and should the smoke not obscure the view of the sky too much) with lows in the mid to upper 40s. Northwest flow develops over the region early next week with periodic disturbances creating chances for showers and afternoon storms. The best chances for storms will be Monday night into Tuesday as a shortwave crosses the northern plains. Better moisture, higher CAPE of 1000-2000 J/kg, and bulk shear values of 30 to 40 kts may support a strong to severe storm or two over the BH Monday afternoon and evening with wider spread convection moving through late Monday night as a front crosses the region. Mean troughing persists into midweek with continued chances for showers and perhaps a few afternoon storms each day. Temps will remain rather seasonable with highs in the 70s. && .AVIATION...(For the 00Z TAFS Through 00Z Monday Evening) Issued At 535 PM MDT Sun May 12 2024 Wildfire smoke filtering into the region may cause periods of MVFR visibilities tonight, especially towards central SD. Isolated to scattered thunderstorms will continue this evening before dissipating later in the evening hours. Thunderstorms will mainly be around northeast Wyoming, the Black Hills area, and near the Nebraska/South Dakota border. Lower flight conditions and erratic and gusty winds are possible near any storms. Storm chances will diminish after sunset. Elsewhere, VFR conditions expected through the TAF period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION/KEY MESSAGES...Wong AVIATION...13